NASA Scientific and Technical Aerospace Reports

A possible accretion model associated with the ionization instability of quasar disks is proposed to address the growth of
the central black hole harbored in the host galaxy. The evolution of quasars in cosmic time is assumed to change from a highly
active state to a quiescent state triggered by the S-shaped ionization instability of the quasar accretion disk. For a given
external mass transfer rate supplied by the quasar host galaxy, ionization instability can modify accretion rate in the disk and
separates the accretion flows of the disk into three different phases, like a S-shape. We suggest that the bright quasars observed
today are those quasars with disks in the upper branch of S-shaped instability, and the faint or ‘dormant’ quasars are simply
the system in the lower branch. The middle branch is the transition state which is unstable. We assume the quasar disk evolves
according to the advection-dominated inflow-outflow solutions (ADIOS) configuration in the stable lower branch of S-shaped
instability, and Eddington accretion rate is used to constrain the accretion rate in each phase. The mass ratio between black
hole and its host galactic bulge is a nature consequence of ADIOS. Our model also demonstrates that a seed black hole (BH)
similar to those found in spiral galaxies today is needed to produce a BH with a final mass 2 x 10(exp 8) solar mases.
Author
Galactic Nuclei; Quasars; Black Holes (Astronomy); Astronomical Models; Ionization
20040074194 Alabama Univ., Huntsville, AL, USA
Dominant Gamma-Ray Bursts Production in the Early Universe
Zhang, S. N.; Lin, J. R.; Li, T. P.; December 2002; 1 pp.; In English
Contract(s)/Grant(s): NAG5-7927; No Copyright; Avail: Other Sources; Abstract Only
It has been known that at least some of the observed gamma-ray bursts (GRBs) are produced at cosmological distances
and the GRB production rate may follow the star formation rate. Here we report that the lower and upper distance limits to
the GRB production are z approx. 0.24 and z approx. 10, respectively. This result suggests that GRBs are no longer produced
presently, and that the actual star formation rate peaks at much higher redshift and thus the ‘dark ages’ of the universe have
ended much earlier than believed previously. This study is supported in part by the Special Funds for Major State Basic
Research Projects and by the National Natural Science Foundation of China. SNZ also acknowledges supports by NASA’s
Marshall Space Flight Center and through NASA’s Long Term Space Astrophysics Program.
Author
Gamma Ray Astronomy; Gamma Ray Bursts
20040074197 Katholieke Univ. te Leuven, Belgium
How Do The Relativistic Effects Effect the Appearance of a Clothed Black Hole?
Zhang, Xiaoling; Zhang, S. N.; Feng, Yuxin; Yao, Yangsen; April 23, 2002; 1 pp.; In English; No Copyright; Avail: Other
Sources; Abstract Only
For an accretion disk around a black hole, the strong relativistic effects affect every aspect of the radiation from the disk,
including the spectrum, the light-curve, and the image. If the disk is in high inclination angle (nearly edge-on), the image will
be greatly distorted; the farther side of the disk will appear to bend toward the observer, photons from the other side of the
disk can reach the observer (if they are not blocked by the disk) to form a ghost image. This work differs mainly from previous
work by taking into account the temperature distribution of a standard thin disk model and investigating the expected images
from different viewing angles and in different energy bands. The edge-blocking effect is also considered. Direct images of
black hole systems may be obtained with future X-ray missions like MAXIM pathfinder.
Author
Relativistic Effects; Black Holes (Astronomy)
20040074203 Smithsonian Astrophysical Observatory, Cambridge, MA, USA
Properties of Minor Ions in the Solar Wind and Implications for the Background Solar Wind Plasma
Wagner, William, Technical Monitor; Esser, Ruth; May 2004; 6 pp.; In English
Contract(s)/Grant(s): NAG5-10996; No Copyright; Avail: CASI; A02, Hardcopy
The scope of the investigation is to extract information on the properties of the bulk solar wind from the minor ion
observations that are provided by instruments on board NASA space craft and theoretical model studies. Ion charge states
measured in situ in interplanetary space are formed in the inner coronal regions below 5 solar radii, hence they carry
information on the properties of the solar wind plasma in that region. The plasma parameters that are important in the ion
forming processes are the electron density, the electron temperature and the flow speeds of the individual ion species. In
addition, if the electron distribution function deviates from a Maxwellian already in the inner corona, then the enhanced tail
of that distribution function, also called halo, greatly effects the ion composition. This study is carried out using solar wind
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